The present invention generally relates to the field of digital image processing and, more specifically, to a video image coding device for encoding digital image data with high efficiency and a video image decoding device for decoding coded data encoded by the video image coding device.
A video image coding method represented by a video image coding system H.261 has been applied for coding video images for video conferences, video telephones and so on. FIG. 1(A) is a block diagram of an exemplary conventional video image coding device and FIG. 1(B) is a block diagram of an exemplary conventional video image decoding device.
In FIG. 1(A), the video image coding device comprises a differencing portion 101, a coding portion 102, an adder 103, a frame memory 104 and a motion-compensated predicting portion 105. In FIG. 1(B), the video image decoding device comprises a decoding portion 106, an adder 107, a frame memory 108 and a motion-compensated predicting portion 109.
An original image is divided into plural blocks, each of which is input to the differencing portion 101 that in turn determines difference data between each block image data and predicted image data input from the motion-compensated predicting portion 105. The predicted image data can be obtained by the motion-compensated prediction from decoded image data that is already encoded and stored in the frame memory 104. At this time, the motion between the decoded image data and the original image data is detected on a block-by-block basis and detected motion data (not shown) is encoded by the coding portion 102. The coding portion 102 also encodes difference data calculated by the differencing portion 101, outputs the coded data and decodes the coded difference data. The decoded difference data is added by the adder 103 to the predicted image data, and then the resultant data is stored in the frame memory 104. The stored decoded data is used for motion-compensated prediction of a subsequent frame.
The decoding portion 106 decodes the coded data to obtain difference data and motion data (not shown). The decoded difference data is added by the adder 107 to the prediction image data and the resultant data is stored in the frame memory 108. The motion-compensated predicting portion 109 generates a predicted image data based on decoded image data stored in the frame memory 108 and the motion data.
Thus, the video images are encoded and decoded as mentioned above.
As the conventional video telephones and video conferencing facilities are usually used indoors, a background image behind a speaking person is generally a still picture. However, with a video telephone using outdoors, a background picture may temporally vary much more than the person""s figure. Even in case of using video telephone indoors, its background image may considerably vary due to movement of a camera or/and with another person passing behind the speaking person. This produces information on the motion of the background image.
In such cases, the conventional technique requires increasing of a total of bits for encoding an entire sequence because of a larger amount of the background information to be encoded under the condition of maintaining a desired frame rate (the number of frames per second). As a result, we have one problem that the transmission capacity of a channel may be exceeded. On the other hand, it is necessary to reduce the frame rate in order to decrease the number of bits for encoding under the condition of maintaining the desired frame image quality. This is also a problem.
To solve the above-mentioned problem, Japanese Laid-Open Patent Publication No. 9-9233 discloses a technique for updating a partial region of each input image by controlling an input image through a video camera. This technique has, however, such a problem that because of appropriating a partial region merely by rectangles, non-continuity of an image occurs around the rectangular region boundary, resulting in considerable deterioration of the decoded image quality.
What is desired, therefore, is a video image coding device and decoding device that are free from the above-described drawbacks of the prior arts and can maintain both desirable frame rate and image quality of the objective (human facial) image without deterioration of the quality of the video image.
Accordingly, an object of the present invention is to provide a video image coding device having a first coding mode for encoding an image within a first region and a second coding mode for encoding an image within a second region being a part of the first region, which comprises a region selecting portion for selecting the first region and the second region, a shape coding portion for encoding the shapes of the first and second regions, a video image coding portion for encoding only the values of pixels inside the selected region according to the output of the shape coding portion and a coding data integrating portion for integrating the outputs of the shape coding portion and the video image coding portion.
Another object of the present invention is to provide a video image coding device having a first coding mode for encoding an image within a first region covering an entire input image and a second coding mode for encoding an image within a second region being a part of the first region, which comprises a region selecting portion for selecting a second region, a shape coding portion for encoding the shape of the second region, a video image coding portion for encoding the values of pixels of the entire image or only pixels inside the second region according to the output of the shape coding portion and a coding data integrating portion for integrating the outputs of the shape coding portion and the video image coding portion.
Another object of the present invention is to provide a video image coding device having a first coding mode for encoding an image within a first region and a second coding mode for encoding an image within a second region being a part of the first region, which comprises a region selecting portion for selecting a first region and a second region and a video image coding portion for encoding, as an ineffective block, a block outside the selected region according to the output of the region selecting portion and also for encoding the information indicative of an ineffective (inert) block and an effective (active) block.
Another object of the present invention is to provide a video image coding device having a first coding mode for encoding an image within a first region covering an entire input image and a second coding mode for encoding an image within a second region being a part of the first region, which comprises a region selecting portion for selecting a second region and a video image coding portion for encoding, as an ineffective block, a block outside the selected region according to the output of the region selecting portion and also for encoding information indicative of an ineffective block/an effective block.
Another object of the present invention is to provide a video image coding device characterized in that in said video image coding portion, coded data is provided with additional information indicating whether a partial region image data coded in the second coding mode is overlapped with an image encoded in the first coding mode.
A further object of the present invention is to provide a video image decoding device having a first decoding mode for decoding an image within a first region and a second decoding mode for decoding an image within a second region being a partial region within first region, which comprises a shape decoding portion for decoding the coded data of the shapes of the first and second regions included in input coded image, a video image decoding portion for decoding only the values of pixels inside the first region in the first decoding mode and only the values of pixels inside the second region in the second decoding mode and an image data overlapping portion for overlapping each other image data decoded in the video image decoding portion.
Another object of the present invention is to provide a video image decoding device having a first decoding mode for decoding a first region covering an entire input image and a second decoding mode for decoding an image within a second region being a partial region within the first region, which comprises a shape decoding portion for decoding coded data of the shape of the second region included in input coded data, a video image decoding portion for decoding the values of pixels of the entire image in the first decoding mode and only the values of pixels inside the second region in the second decoding mode and an overlapping portion for overlapping with each other image data decoded in said video image decoding portion.
Another object of the present invention is to provide a video image decoding device having a first decoding mode for decoding an image within a first region and a second decoding mode for decoding an image within a second region being a partial region within the first region, which comprises a video image decoding portion for decoding only the values of pixels inside the first region in the first decoding mode and only the values of pixels inside the second region in the second decoding mode according to ineffective/effective block information included in input coded data as information of whether the data being inside the first region or the second region and an overlapping portion for overlapping with each other image data decoded in said video image decoding portion.
Another object of the present invention is to provide a video image decoding device having a first decoding mode for decoding an image in a first region covering an entire image and a second decoding mode for decoding an image within a second region being a partial region within the first region, which comprises a video image decoding portion for decoding the values of pixels of the entire image in the first decoding mode and only the values of pixels inside the second region in the second decoding mode according to ineffective/effective block information included in the input coded data as information indicative of whether data being inside the first region or the second region and an overlapping portion for overlapping with each other image data decoded in said video decoding portion.
Another object of the present invention is to provide a video image decoding device characterized in that in said overlapping portion, image data decoded in the second decoding mode is overlapped with the image data decoded in the first decoding mode or another image data based upon information indicating whether a partial regional image data coded in the second coding mode is overlapped with an image coded in the first coding mode.